1. Field of the Disclosure
This invention is related to image sensors, and more particularly, to color filter arrays for use in color image sensors.
2. Background
Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors, and in particular, complementary metal-oxide-semiconductor (CMOS) image sensors (CIS), has continued to advance at a great pace. For example, the demands for higher resolution and lower power consumption have encouraged the further miniaturization and integration of these image sensors.
In conventional color image sensors, incident light is typically directed through microlenses and then through color filters of a color filter array to pixel cells of a pixel array. The pixel cells include photosensitive elements to convert the incident light into electrical signals that are proportional to the intensity of the incident light. Color image sensors use the color filter arrays to help capture the color information in the incident light. A color filter array includes a pattern of different colored filters to filter the light that reaches each pixel cell in the underlying color image sensor.
As the pixel cell sizes in color image sensors become smaller, it becomes increasingly challenging for the microlenses to focus all of the incident light through specific color filters of the color filter array to the underlying pixel cells. As a result, there can be undesired crosstalk among the underlying color filters as light that is directed into one color filter ends up leaking into a different unintended color filter in the color filter array. This also causes unwanted crosstalk among the underlying pixel cells. Crosstalk among the color filters in a color filter array, and/or among the underlying pixel cells in the pixel array creates undesirable noise in the image sensor and therefore degrades overall image quality of images captured by the image sensor.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.